21304681 has 8 divisors (see below), whose sum is σ = 22626720. Its totient is φ = 20002752.

The previous prime is 21304667. The next prime is 21304697. The reversal of 21304681 is 18640312.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21304681 - 2¹³ = 21296489 is a prime.

It is a super-2 number, since 2×21304681² = 907778865023522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21304081) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2815 + ... + 7108.

It is an arithmetic number, because the mean of its divisors is an integer number (2828340).

Almost surely, 2^21304681 is an apocalyptic number.

It is an amenable number.

21304681 is a deficient number, since it is larger than the sum of its proper divisors (1322039).

21304681 is a wasteful number, since it uses less digits than its factorization.

21304681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10055.

The product of its (nonzero) digits is 1152, while the sum is 25.

The square root of 21304681 is about 4615.6994052906. The cubic root of 21304681 is about 277.2202889962.

Adding to 21304681 its reverse (18640312), we get a palindrome (39944993).

The spelling of 21304681 in words is "twenty-one million, three hundred four thousand, six hundred eighty-one".